High-voltage direct current power supply system for an aircraft

ABSTRACT

The invention provides an electrical power supply system for an aircraft, the system comprising: a first electrical power supply network ( 1 ) including a first alternator ( 10 ); a second electrical power supply network ( 2 ) including a second alternator ( 20 ); and secondary lines ( 40 ) united in at least a first group ( 41 ) such that they are connected via switches to a common first intermediate line ( 51 ), and in at least a second group ( 42 ) so as to be connected via switches to a common second intermediate line ( 52 ); the system including a control member ( 60 ) for controlling the electrical power supply networks, the control member being arranged to servo-control each of the alternators in current, the system being arranged in such a manner that the power supply outputs of the two electrical power supply networks are connected together prior to being connected to each intermediate line, each intermediate line thus being powered in parallel by the two electric power supply networks.

The invention relates to a high voltage direct current (HVDC) electricalpower supply system for an aircraft.

TECHNOLOGICAL BACKGROUND OF THE INVENTION

In order to reduce the fuel consumption of an aircraft, it is becomingmore and more frequent to replace traditional devices that are driven byhydraulic energy or by pneumatic energy with novel devices that aredriven by electrical energy.

With an aircraft operating mainly on the basis of electrical energy,numerous devices need to be able to access the electrical power supplysystem of said aircraft.

OBJECT OF THE INVENTION

An object of the invention is to propose a high voltage direct currentelectrical power supply system for an aircraft, which system presentsvery good availability.

BRIEF SUMMARY OF THE INVENTION

In order to achieve this object, the invention provides a high voltagedirect current electrical power supply system for an aircraft, thesystem comprising at least:

-   -   a first electrical power supply network including a first        alternator;    -   a second electrical power supply network including a second        alternator; and    -   secondary lines for electrically powering elements of the        aircraft, the secondary lines being united in at least a first        group so as to be connected via switches to a common first        intermediate line, and in at least a second group so as to be        connected via switches to a common second intermediate line;    -   the system including a control member for controlling the        electrical power supply networks, the control member being        arranged to servo-control each of the alternators in current,        the system being arranged in such a manner that the power supply        outputs of the two electrical power supply networks are        connected together prior to being connected to each intermediate        line, each intermediate line thus being powered by the two        electrical power supply networks and the two intermediate lines        being powered in parallel.

By servo-controlling the various alternators in current, the alternatorscan power each intermediate line in parallel and can thus power eachgroup of secondary lines.

It is thus possible for the control member to define a current controlsetpoint for each of the networks so that each network supplieselectrical power at its output that is a function of the needs of thevarious groups of secondary lines and of the availabilities of eachnetwork, which may vary as a function of the operational state of thenetworks or indeed as a function of flight parameters, for example.

The overall electrical power supply system of the invention thuspresents good availability since the control member acts on the presenceof a plurality of networks and on connecting said networks in parallelso as to ensure that suitable electrical power is supplied to thesecondary lines, even if there are variations in the availabilityspecific to each network.

Advantageously, it is found possible to modify the way electrical poweris supplied by each of the networks to the secondary lines in a mannerthat is progressive. This makes it possible to avoid jumps anddisturbances in the electrical power supply system.

Furthermore, it is found advantageous to servo-control the alternatorsin current since the alternators operate naturally in current.

Furthermore, the failure rate of the power supply system of theinvention is low since each group of secondary lines is connected toeach of the available networks.

In addition, the power supply system of the invention makes it possibleto minimize the noise generated by the networks.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be better understood in the light of the followingdescription of a particular, non-limiting embodiment of the invention.Reference is made to the accompanying figures, in which:

FIG. 1 is a diagram showing the electrical power supply system of theinvention; and

FIG. 2 is a diagram showing a portion of the system shown in FIG. 1, ingreater detail.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIG. 1, the HVDC electrical power supply system of theinvention for an aircraft comprises in this embodiment:

-   -   a first electrical power supply network 1 having a first        alternator 10;    -   a second electrical power supply network 2 having a second        alternator 20; and    -   a third electrical power supply network 3 having a third        alternator 30.

Typically, the first alternator 10 is associated with a first mainengine of the aircraft (not shown herein) with the first alternator 10converting mechanical energy delivered by the first main engine intoalternating current (AC) electrical energy. The second alternator 20 isassociated with a second main engine of the aircraft (not shown herein),the second alternator 20 converting mechanical energy delivered by thesecond main engine into AC electrical energy. Finally, the thirdalternator 30 is associated with an auxiliary power unit (APU) of theaircraft (not shown herein), the third alternator 30 convertingmechanical energy delivered by the APU into AC electrical energy. Inthis embodiment, all three alternators 10, 20, and 30 haveelectromagnets rather than permanent magnets. More precisely, all threealternators 10, 20, and 30 are controlled excitation three-phasealternators.

The first electrical power supply network 1 thus has the firstalternator 10 connected to a first rectifier 11. The output from thefirst rectifier 11 is in turn connected to a first lowpass filter 12.The output from the first lowpass filter 12 is connected in parallel tothree switches 13 a, 13 b, and 13 c, respectively defining a firstoutput 14 a of the first network 1, a second output 14 b of the firstnetwork 1, and a third output 14 c of the first network 1.

Likewise, the second electrical power supply network 2 comprises thesecond alternator 20 connected to a second rectifier 21. The output fromthe second rectifier 21 is in turn connected to a second lowpass filter22. The output from the second lowpass filter 22 is connected inparallel to three switches 23 a, 23 b, and 23 c, respectively defining afirst output 24 a of the second network 2, a second output 24 b of thesecond network 2, and a third output 24 c of the second network 2.

Finally, the third electrical power supply network 3 comprises the thirdalternator 30 connected to a third rectifier 31. The output from thethird rectifier 31 is in turn connected to a third lowpass filter 32.The output from the third lowpass filter 32 is connected in parallel tothree switches 33 a, 33 b, and 33 c, respectively defining a firstoutput 34 a of the third network 3, a second output 34 b of the thirdnetwork, and a third output 34 c of the third network.

Furthermore, the electrical power supply system has a plurality ofsecondary lines 40 for electrically powering various elements of theaircraft. In this embodiment, the secondary lines are united in:

-   -   a first group 41 such that each secondary line 40 of said group        is connected in parallel via an associated switch 44 to a common        first intermediate line 51;    -   a second group 42 such that each secondary line 40 of said group        is connected in parallel via an associated switch 45 to a common        second intermediate line 52; and    -   a third group 43 such that each secondary line 40 of said group        is connected in parallel via an associated switch 46 to a common        third intermediate line 53.

The system is also arranged in such a manner that the first output 14 aof the first electrical power supply network 1, the first output 24 a ofthe second electrical power supply network 2, and the first output 34 aof the third electrical power supply network 3 are connected togetherprior to being connected to the first intermediate line 51. Because thethree first outputs 14 a, 24 a, and 34 a are connected together, thevoltage across the terminals of the first intermediate line 51 is anHVDC voltage (for High Voltage Direct Current).

Likewise, the system is arranged in such a manner that the second output14 b of the first electrical power supply network 1, the second output24 b of the second electrical power supply network 2, and the secondoutput 34 b of the third electrical power supply network 3 are connectedtogether prior to all of them being connected together to the secondintermediate line 52. The voltage across the terminals of the secondintermediate line 52 is thus an HVDC voltage.

In addition, the system is arranged in such a manner that the thirdoutput 14 c of the first electrical power supply network 1, the thirdoutput 24 c of the second electrical power supply network 2, and thethird output 34 c of the third electrical power supply network 3 areconnected together prior to all of them being connected to the thirdintermediate line 53. The voltage across the terminals of the thirdintermediate line 53 is an HVDC voltage.

Thus, each intermediate line 51, 52, and 53 is powered by all threeelectrical power supply networks 1, 2, and 3. In addition, the threeintermediate lines 51, 52, and 53 are powered in parallel by saidelectrical power supply networks 1, 2, and 3. The switches 44, 45, and46 of the various groups 41, 42, and 43 of secondary lines then enableelectrical power to be redistributed to the various elements.

The system also has a control member 60 for controlling the threeelectrical power supply networks 1, 2, and 3. The control member 60 isthus arranged to servo-control each of the three alternators 10, 20, and30 in current. This current servo-control serves to make it very easy toconnect the three alternators 10, 20, and 30 in parallel, and thus thethree networks 1, 2, and 3, in parallel.

The control member 60 thus has reception means 61 for receiving adistribution setpoint 62 for distributing the electrical power to besupplied to the intermediate lines 51, 52, and 53 by each electricalpower supply network 1, 2, and 3. By way of example, the distributionsetpoint 62 is issued by an on-board computer of the aircraft. Thereception means 61 are configured to decouple the distribution setpoint62 into:

-   -   a first setpoint 71 for the first electrical power supply        network 1;    -   a second setpoint 72 for the second electrical power supply        network 2; and    -   a third setpoint 73 for the third electrical power supply        network 3.

The reception means 61 are configured so that the first setpoint 71, thesecond setpoint 72, and the third setpoint 73 are all in the form of apercentage (lying in the range 0 to 100%) corresponding to theelectrical power that is to be supplied by the corresponding electricalpower supply network to the various intermediate lines 51, 52, and 53,and in such a manner that the sum of the first setpoint 71 plus thesecond setpoint 72 plus the third setpoint 73 is always 100%.

The control member includes means for measuring the voltages across theterminals of the three intermediate lines 51, 52, and 53. The voltagesacross the terminals of the various intermediate lines 51, 52, and 53are identical and equal to the HVDC voltage, so multiple measurementsare therefore taken for reasons of redundancy.

The control member 60 has comparator means 63 for comparing the voltagemeasured across the terminals of any one of the intermediates lines 51,52, or 53, e.g. across the terminals of the first intermediate line,with a reference threshold voltage 64. The comparator means 63 amplifythe error between the measured voltage and the reference voltage 64 andsupply an amplified error 65 to the input of a first multiplier 81 ofthe control member 60, to the input of a second multiplier 82 of thecontrol member 60, and to the input of a third multiplier 83 of thecontrol member 60.

The first multiplier 81 multiplies said amplified error 65 by the firstsetpoint 71, after passing the first setpoint 71 through a lowpassfilter 66 of the control member 60, so as to generate a first voltagecontrol setpoint 91 for the first electrical power supply network 1. Thecontrol member 60 also has a first voltage-to-current converter 101connected to the first multiplier 81 so as to transform said firstvoltage control setpoint 91 into a first current control setpoint 111that is transmitted directly to the first alternator 10. More precisely,the first current control setpoint 111 is transmitted to the powersupply generator 121 of the excitation winding of the first alternator10.

Likewise, the second multiplier 82 multiplies said amplified error 65 bythe second setpoint 72 after passing the second setpoint 72 through alowpass filter 67 of the control member 60 so as to generate a secondvoltage control setpoint 92 for the second electrical power supplynetwork 2. The control member 60 also has a second voltage-to-currentconverter 102 connected to the second multiplier 82 so as to transformsaid second voltage control setpoint 92 into a second current controlsetpoint 112 that is transmitted directly to the second alternator 20.More precisely, the second current control setpoint 112 is transmittedto the power supply generator 122 of the excitation winding of thesecond alternator 20.

Likewise, the third multiplier 83 multiplies said amplified error 65 bythe third setpoint 73 after passing the third setpoint 73 through alowpass filter 68 of the control member in order to generate a thirdvoltage control setpoint 93 for the third electrical power supplynetwork 3. The control member 60 also has a third voltage-to-currentconverter 103 connected to the third multiplier 83 so as to transformsaid third voltage control setpoint 93 into a third current controlsetpoint 113 that is transmitted directly to the third alternator 30.More precisely, the third current control setpoint 113 is transmitted tothe power supply generator 123 of the excitation winding of the thirdalternator 30.

As a result, depending on the distribution setpoint 62 and on themeasured voltage, the control member 60 serves to generate currentcontrol setpoints 111, 112, and 113 for each of the alternators 10, 20,and 30 of the three electrical power supply networks 1, 2, and 3. Thecontrol member 60 thus uses a servo-control loop having as inputs thedistribution setpoint 62 and the measured voltage, and having as outputsthe three current control setpoints 111, 112, and 113.

Furthermore, the filtering of the first setpoint 71, of the secondsetpoint 72, and of the third setpoint 73 by a respective lowpass filter66, 67, or 68 serves to avoid changes to the setpoints giving rise todisturbances in the above-described servo-control loop.

In addition, causing the alternators 10, 20, and 30 to operate undercurrent control makes it possible to avoid problems of drift in thecharacteristics of the excitation windings of said alternators 10, 20,and 30.

Preferably, the control member 60 has means for detecting excess voltageon each of the electrical power supply networks 1, 2, and 3 so as toprovide indications 69 of any excess voltage in the various networks 1,2, and 3 to the control member 60.

The control member 60 can thus adapt the various setpoints 71, 72, and73 so as to avoid the excess voltage lasting in any of the associatednetworks 1, 2, and 3.

Preferably, the control member 60 has a capacitor 70 with the voltageacross its terminals being the HVDC voltage, the capacitor 70 beingarranged at the input of the control member 60. The role of thecapacitor 70 is to assist in stabilizing said HVDC voltage duringcurrent transients and also to assist in stabilizing the above-describedservo-control loop.

Preferably, the control member 60 servo-controls the three alternators10, 20, and 30 in current so that it is the first network 1 and thesecond network 2, i.e. the networks that are associated with the mainengines, that supply electrical power as a priority to the variousintermediate lines 51, 52, and 53, with the third network 3 acting as anadjustment variable when the first network 1 and the second network 2cannot on their own supply the electrical power to the variousintermediate lines 51, 52, and 53.

Thus, by means of the invention, the control member 60 performsservo-control that makes it possible to distribute the supply ofelectrical power by each of the networks 1, 2, and 3 in a manner that isdynamic as a function in particular of the availability of each network1, 2, and 3.

By means of these three distinct networks 1, 2, and 3, and by means ofthe various switches 13 a, 13 b, 13 c, 23 a, 23 b, 23 c, 33 a, 33 b, and33 c, it is possible to decide which electrical power supply network 1,2, and 3 is to power each of the groups 41, 42, and 43 of secondarylines, and in what proportions. Nevertheless, it is preferable to ensurethat any modification to the power delivered by each of the networks 1,2, and 3 to the intermediate lines 51, 52, and 53 is modifiedprogressively by the control member 60 whenever it opens one or moreswitches 13 a, 13 b, 13 c, 23 a, 23 b, 23 c, 33 a, 33 b, and 33 c, so asto avoid generating any disturbances in the system.

Naturally, the invention is not limited to the embodiment described, andembodiment variants may be applied thereto without going beyond theambit of the invention as defined by the claims.

In particular, although the power supply system described has threeelectrical power supply networks, each having only one alternator, theelectrical power supply system could have some other number ofalternators, providing it has at least two.

The invention claimed is:
 1. A high voltage direct current electrical power supply system for an aircraft, the system comprising at least: a first electrical power supply network including a first alternator; a second electrical power supply network including a second alternator; and secondary lines for electrically powering elements of the aircraft, wherein the secondary lines are united in at least a first group so as to be connected via switches to a common first intermediate line, and in at least a second group so as to be connected via switches to a common second intermediate line; and wherein the system includes a control member for controlling the electrical power supply networks, the control member being arranged to servo-control each of the alternators in current, the system being arranged in such a manner that first power supply outputs of the two electrical power supply networks are connected together prior to being connected to the first intermediate line and so that second power supply outputs of the two electrical power supply networks, distinct from the first outputs, are connected together prior to being connected to the second intermediate line, each intermediate line thus being powered by the two electrical power supply networks and the two intermediate lines being powered in parallel.
 2. The system according to claim 1, wherein the control member includes reception means for receiving a distribution setpoint for the electrical power to be supplied to the intermediate line by each electrical power supply network and for receiving a measurement of voltage across the terminals of at least one of the intermediate lines, the control member being configured to generate current control setpoints for each of the alternators as a function of said distribution setpoints and of said voltage measurement.
 3. The system according to claim 2, wherein the control member also includes detector means for detecting excess voltage in each of the electrical power supply networks and in communication with the control member.
 4. The system according to claim 2, wherein the reception means decouple the distribution setpoint into a first setpoint for the first network and a second setpoint for the second network.
 5. The system according to claim 4, wherein the control member has two multipliers, the first multiplier being configured to multiply the first setpoint by an error between the voltage measurement and a threshold voltage, and the second multiplier being configured to multiply the second setpoint by said error between the voltage measurement and the threshold voltage.
 6. The system according to claim 5, wherein the control member includes a first voltage-to-current converter connected to the output from the first multiplier, and a second voltage-to-current converter connected to the output of the second multiplier.
 7. The system according to claim 1, wherein each electrical power supply network comprises one of the first or the second alternators, a rectifier connected to the first or the second alternator, a lowpass filter connected to the rectifier, and at least two switches connected in parallel to the lowpass filter, the outputs from the switches being connected to respective ones of the intermediate lines.
 8. The system according to claim 1, wherein one of the alternators is connected to an auxiliary power unit of the aircraft.
 9. The system according to claim 1, having three electrical power supply networks, each having an alternator, the secondary lines being united in three groups, each connected to a common intermediate line via switches, the system being arranged in such a manner that each intermediate line is powered in parallel by each of the three electrical power supply networks. 